I have written at length about the importance of “reptilian brain,” the primitive part of the brain that is heavily involved in eating, breathing, habits, reflexes, and comfort. Scientists have known the importance the reptilian brain for more than a century, but we are just now learning the significance of the enteric nervous system, the “second brain” that is located along the intestines. Scientists always figured that this brain was involved in controlling the digestive process, and was the source of the gut feelings that so often reflect a form of wisdom that isn’t available to us intellectually. But it turns out that the brain in the gut is much more than this. A new Scientific American online story written by Adam Hadhazy outlines some of the latest information on the “second brain.”
At the risk of taking some license with the known scientific facts, I think of the “second brain” as the “worm brain.” I don’t really know how a worm’s brain works, but the shape of the enteric nervous system resembles that of a worm, so I am imagining that there are functional parallels.
It is apparent that the “second brain” has qualities that the brain in the head cannot imitate. The gut is 9 meters long. The head’s neurons are much more closely interconnected and because of this, the head comes to conclusions sooner. The gut takes longer to come to any conclusion.
The gut communicates with bacteria — the huge numbers of bacteria in the intestine, more numerous than the number of neurons in the entire human body — and it appears to draw significant information from them. There is no indication that the head has any such ability, and scientists at this point can only imagine the information that the gut receives from bacteria, and how the communication takes place.
The gut is also more involved in mental states and in diseases than was previously imagined. The Scientific American story mentions intriguing hints that depression and autism may originate in the gut. Serotonin, a neurotransmitter with profound effects on the thinking process, mostly originates in the gut, and scientists recently found a way to cure osteoporosis in rodents by inhibiting this process.
All this new information has made me more interested than I was already in the interaction between food and mood. Food surely must affect human moods in a profound way, and potentially very quickly, and mood in turn may determine many food choices. This forms a cycle that, if we are not careful, can proceed without any conscious control. Conscious control of patterns of food and mood, to the extent that we are able to develop it, would start with paying more attention to these connections.